A Known liquid crystal display includes a liquid crystal cell, a polarizing film, and an optical film for optical compensation (also referred to as an optically-compensatory film or retardation film).
A transparent liquid crystal display includes two polarizing films on both surfaces of a liquid crystal cell, and one or more optically-compensatory films between the liquid crystal cell and the polarizing films. A reflective liquid crystal display has, in sequence, a reflector, a liquid crystal cell, an optically-compensatory film, and a polarizing film. A liquid crystal cell consists of rod-like liquid crystal molecules, two substrates encapsulating the molecules, and electrode layers for applying voltage to the molecules. Liquid crystal cells are categorized into various display modes by the alignment states of their rod-like liquid crystal molecules. For instance, transparent displays are present in various display modes, such as twisted nematic (TN), in-plane switching (IPS), ferroelectric liquid crystal (FLC), optically compensatory bend (OCB), super twisted nematic (STN), vertically aligned (VA), and electrically controlled birefringence (ECB) modes. Reflective displays are present in TN cells, hybrid aligned nematic (HAN) and guest-host (GH) modes.
Optically-compensatory films are used in various liquid crystal displays to avoid coloring of images or increase the viewing angles. Traditional optically-compensatory films include stretched birefringent polymer films. As an alternative for an optical compensatory film composed of a stretched birefringent film, optically-compensatory films are currently proposed which include an optically anisotropic layer consisting of a support coated with an aligned liquid crystal compound. Liquid crystal compounds have a variety of alignment states and thus can provide optical properties that cannot be accomplished by traditional stretched birefringent polymer films.
The optical properties of an optically-compensatory film depend on the optical properties or display mode of the liquid crystal cell. The use of a liquid crystal compound allows for the manufacture of an optically-compensatory film having different optical properties suitable for various display modes of the liquid crystal cell. Examples of such an optically-compensatory film include a laminate of two optically anisotropic layers, which is disclosed in Japanese Unexamined Patent Application Publication No. 2000-304930.
In particular, Japanese Unexamined Patent Application Publication No. 2000-304930 discloses an optically-compensatory film in FIG. 6 including, in sequence, a support 1′, a rubbed first alignment film 2′, a first optically anisotropic layer 3′, a rubbed second alignment film 2′, and a second optically anisotropic layer 4′, the second alignment film 2′ being on the first optically anisotropic layer 3′ and aligning liquid crystal compounds in the second optically anisotropic layer 4′.